[Swordmaker]

I wonder if the much higher oxygen content of the air could support cellular function while reducing other requirements having to do with structure and function. Maybe the velociraptor wasn’t really that fast and everything was sort of a molassass world.

Couple of problems I see right off the bat... if the atmosphere were thicker, more dense, then the animals would be adapted to be more aerodynamic than we find them. Large animals with sails like the Dimetradon:

Would only be able to walk into or away from the wind... and cross wind walking would be impossible... if not downright hilarious.

[aruanan]

Maybe the velociraptor wasn’t really that fast and everything was sort of a molassass world.

I was referring only to movement of animals, not to density of air. I remember asking one of Paul Sereno's grad students about the higher oxygen content way back then. He acknowledged it but didn't have much to say.